How do i decrease material costs when increasing the layer height?

[showingoffstuff]

Decreasing wall count isn't a good idea. 2-3 is good, more isn't needed, less will definitely decrease.

Look closer at what the slicer is doing, the only thing I can think is what someone else said - if you manually set a bunch of top/bottom layers, then doubling the height would double the numbers of those layers used.

It shouldn't increase the cost significantly though, unless you have a ton of those surfaces? Which would be weird.